1. Field of Invention
The present invention relates to fast and realistic printing and, more particularly, to reduction of data with limited distortion of an image formed of the data.
2. Related Prior Art
A typical printing system includes a printer and a computer. At least one sort of application software and a printer driver are run in the computer. Printer firmware is run in the printer. A print job is formed and rendered in the application software run in the computer page by page. Each page may include at least one graphic object, at least one image object and/or at least one text object. Then, the print job is processed in the printer driver run in the computer. The print job is sent from the computer to the printer through a cable. The print job is processed in the printer firmware run in the printer. Finally, the print job is printed on a destination surface such as the surface of a piece of paper.
Speed and quality are important criteria for evaluating printers. Although dreaming of an ideal printing system that can print well and fast, we often have to sacrifice quality in pursuit of speed, and vice versa. Therefore, what we really do is try to achieve a balance between quality and speed.
Printing time includes rendering time, transferring time and processing time. The rendering time is spent to convert graphic objects, image objects and/or text objects into commands and data. For an image object, the rendering time often includes compression time. The rendering time is substantially dependent on the central processing unit used in the computer and often makes a small portion of the printing time. The transferring time is spent to transfer the commands and data from the computer to the printer through the cable and is substantially determined by the printer driver run in the computer. The transferring time often makes the greatest portion of the printing time. This becomes more apparent when the print job grows larger. To reduce the transferring time, there are several options: reducing the size of the commands and data to be transferred from the computer to the printer through the cable, using a more efficient network transfer protocol and improving the speed of the hardware of the printing system including the printer, the computer and the cable. The processing time is spent to decompress, interpret and realize the commands and data on the destination surface, and is dependent on the printer firmware. To reduce the processing time, there are several options: using a more efficient data-compressing method and a data-reducing method. A lot of effort has been made on reducing the data to be transferred.
Compression is often used to reduce data to be transferred from a computer to a printer through a cable. There are many data-compressing methods such as Tiff and Delta Row. Tiff compresses a line without knowledge of previous lines. Delta Row compares the differences between a line and a previous line. Tiff seems more efficient than Delta Row in compressing non-true-color images or images with gray-scale levels, while Delta Row seems more efficient than Tiff in compressing true-color images and images in which reproduction of a line occurs frequently. To select the best one from several data-compressing methods is important. However, there has not been any method known that can select the best one from several data-compressing methods.
Even if an adequate data-compressing method can be found, the data may still be too large for transmission after compression.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.